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1.
The imaging characteristics of diagnostic ultrasound (US) are determined by the ultrasonic properties of tissue. The velocity of propagation of US and the attenuation are the 2 most important parameters. These determine the frequency with which the tissues may be imaged, which in turn sets a fundamental limit on the axial and the lateral resolution. Ultrasonic imaging equipment is designed on the premise that the ultrasonic energy propagates through tissue in a straight line and that the ultrasonic beam is very narrow. In fact, the ultrasonic energy propagates through tissue as a beam of finite dimensions set by the physical dimensions of the transducer, the way it is constructed, and the way it is energized. Also, the velocity of propagation in different tissues varies and this can lead to deviation of the ultrasonic beam from the assumed direction of propagation. This breakdown in assumptions leads to the creation of artifacts that must be appreciated in the interpretation of ultrasonic images. For this reason skilled interpreters of ultrasonic images follow 3 golden rules: never make an interpretation on a single image; just because a feature is displayed do not consider that it is necessarily real; and just because a feature is not displayed do not consider that it is necessarily not there.  相似文献   

2.
肿胀法外超声吸脂术的组织学研究   总被引:7,自引:1,他引:6  
目的 观察外超声能量作用于活体组织后的组织学变化,以探索其作用机制。方法 对3只家猪腹部两侧进行外超声与非超声比较,作用不同时间后在光镜和电镜下观察其皮肤组织全层的变化。结果 在外超声作用18min内,随着作用时间的延长,猪的皮下脂肪组织和生物大分子结构的破坏程度不断加重,脂肪组织中产生的空泡不断增大而皮肤组织及血管无明显变化。结论 外超声吸脂术可通过稳定的空泡效应选择性地使脂肪细胞结构发生不可逆的坏死性改变,这一改变与作用时间成正比。  相似文献   

3.
Vaser® (vibration amplification of sound energy at resonance) lipoabdominoplasty was introduced in the author’s practice in January 2014, and 50 cases have already been treated since then. The author has modified the lipoabdominoplasty introduced by Saldanha in 2006 by applying Vaser® LipoSelection instead of standard liposuction. The main advantage of the ultrasound-assisted device is its ability to target only fat cells, thereby sparing vessels, nerves, and supporting structures of the skin. This ensures a high degree of safety and viability of tissues during a standard body-contouring procedure. In contrast to standard liposuction, which involves blind suction and aspirates fat tissue at the subcutaneous level without differentiating between structures types, Vaser® ultrasound is selective. This is based on the ability of the ultrasound energy to achieve emulsification of only fat cells by means of the physical phenomenon referred to as “cavitation.” In recent years, the author has honed the ability of Vaser® to perform well in superficial subcutaneous tissue; this helps thin the dermal fat layer, allowing the skin to retract to a greater extent than with standard liposuction. To obtain a high degree of skin retraction, the device should be able to perform a close defatting of the superficial fat layer without affecting tissue vascularization.  相似文献   

4.
In vivo transcranial brain surgery with an ultrasonic time reversal mirror   总被引:1,自引:0,他引:1  
OBJECT: High-intensity focused ultrasonography is known to induce controlled and selective noninvasive destruction of tissues by focusing ultrasonic beams within organs, like a magnifying glass concentrating enough sunlight to burn a hole in paper. Such a technique should be highly interesting for the treatment of deep-seated lesions in the brain. Nevertheless, ultrasonic tissue ablation in the brain has long been hampered by the defocusing effect of the skull bone. METHODS: In this in vivo study, the authors used a high-power time-reversal mirror specially designed for noninvasive ultrasonic brain treatment to induce thermal lesions through the skulls of 10 sheep. The sheep were divided into three groups and, depending on group, were killed 1, 2, or 3 weeks after treatment. The thermal lesions were confirmed based on findings of posttreatment magnetic resonance imaging and histological examinations. After treatment, the basic neurological functions of the animals were unchanged: the animals recovered from anesthesia without any abnormal delay and did not exhibit signs of paralysis or coma. No major behavioral change was observed. CONCLUSIONS: The results provide striking evidence that noninvasive ultrasonographic brain surgery is feasible. Thus the authors offer a novel noninvasive method of performing local brain ablation in animals for behavioral studies. This technique may lead the way to noninvasive and nonionizing treatment of brain tumors and neurological disorders by selectively targeting intracranial lesions. Nevertheless, sheep do not represent a good functional model and extensive work will need to be conducted preferably on monkeys to investigate the effects of this treatment.  相似文献   

5.
High intensity ultrasound   总被引:25,自引:0,他引:25  
High-intensity focused ultrasound (HIFU) is a technique that was first investigated in the 1940s as a method of destroying selective regions within the brain in neuro-surgical An ultrasound beam can be brought to a tight focus at a distance from its source, and if sufficient energy is concentrated within the focus, the cells lying within this focal volume are killed, whereas those lying elsewhere are spared. This is a noninvasive method of producing selective and trackless tissue destruction in deep seated targets in the body, without damage to overlying tissues. This field, known both as HIFU and focused ultrasound surgery (FUS), is reviewed in this article.  相似文献   

6.
Ultrasound-assisted lipoplasty (UAL) was developed in Europe and South America. Its introduction into the mainstream of United States surgery in 1997 was initially received with great enthusiasm. Soon, however, anecdotal reports surfaced describing limitations and complications related to the emerging technology. Among the concerns expressed were burns and postoperative seroma formation. The etiology of these complications was speculated to be a result of prolonged ultrasonic energy time. Consequently, some authors recommended limiting the amount of ultrasonic energy time per site and even complete avoidance of UAL in certain body areas. Our review includes over 350 consecutive cases of internal UAL performed by two surgeons utilizing a similar technique. The basic rules of UAL as described by Zocchi were followed without regard to other limitations such as ultrasonic energy site times, body areas, and level of tissue planes. The mechanism of action of UAL and the surgical technique are described. The procedure is a two-stage technique, including tumescent infiltration followed by energy application and simultaneous hollow titanium cannula aspiration. Suction-assisted lipoplasty was not a component of the procedure. The results, including complications, are outlined. Complications were few and not severe. There was no correlation between length of ultrasonic energy time and rate of postoperative complications. The advantages and disadvantages of UAL are discussed. UAL alone is the authors' preferred technique for body contouring to all body areas, except in the female breast.  相似文献   

7.
The hemostasis systems applied in surgery are based on endothermic heat production resulting from the interaction between energy and tissue.The most frequently used energy source is electrocoagulation, applied through two systems: monopolar and bipolar. More sophisticated electrocoagulation systems have progressively been developed such as the Argon beam, in which coagulation is superficial and does not injure the deep tissues, or LigaSure?, based on the use of a bipolar system with an inbuilt feedback system allowing vessels to be sealed without excessive heat and a consequent reduction of collateral lesions.Another system that has been developed in the last few years is the ultrasonic scalpel, based on the ability of the cell membrane proteins to denature as a result of ultrasonic vibration. This system avoids some of the risks involved in the use of electrical energy such as accidental burns due to stray electrical current or faulty insulation of an instrument. Moreover, the harmonic scalpel reaches a temperature of no more than 100° and the effect of lateral tissue destruction is much lower than with electrosurgery, although this reduction is negligible when compared with the electrosurgical methods developed in the last few years such as LigaSure.Another system that is also used is laser energy, consisting of a photon beam containing a specific wavelength; each photon moves in step with the others in both time and space. This system has not become widely used due to its high cost, the difficulty of controlling this type of energy, and the lack of objective advantages over conventional electrosurgery.  相似文献   

8.
The originality of tattoo destruction by ruby laser is to selectively treat the tattooed areas without injuring the surrounding normal cells, in order to obtain better healing. Therefore, we selected a red laser (ruby, emitting at 694.3 nm), with very short flashes (100 ns with self Q switched ruby laser). Ruby laser spots of about 1 cm diameter are delivered to on the area to be treated. As the black particles of the tattoo absorb more laser energy than the surrounding pale-pink skin (140 Mw/cm2, i.e. 14 j/cm2), we can obtain quite localized destruction and better healing. The beam is focussed on one point of the tattoo with a sighting neon-helium laser. In view of the very short impact, the energy absorbed by the pigmented particles diffuses minimally to adjacent tissues. After the crust falls, carrying away some tattoo pigment on its deeper surface, a pale-pink scar forms, then gradually fades in several months. With thick tattoos, it is necessary to proceed in layers and to plan a course of several treatments about one month apart. Compared with the other methods of tattoo removal (dermabrasion, salt, CO2 laser), ruby laser gives the best cosmetic results, even in keloid prone areas.  相似文献   

9.
A technique for performing mucosal proctectomy in patients with ulcerative colitis using ultrasonic fragmentation is described. Twenty-eight patients undergoing colectomy and ileoanal anastomosis were studied. Removal of the mucosal layer of the distal rectum was performed using a titanium probe vibrating at 23 kHZ with an amplitude of 300 microns. This method produces complete mucosal destruction and the resulting debris and irrigating fluid is removed through the hollow central portion of the probe. Healing of the ileoanal anastomosis does not appear to be adversely affected by the use of this technique. Because ultrasonic fragmentation is not dependent on the integrity of the submucosal plane, it may be advantageous in those cases in which severe inflammation and submucosal scarring make manual dissection of the rectal mucosa difficult to perform.  相似文献   

10.
The ultrasonic dissector facilitates laparoscopic cholecystectomy.   总被引:1,自引:0,他引:1  
The ultrasonic dissector disrupts tissues in proportion to their fluid content by ultrasonically induced cavitational forces. Since sturdy tissues are spared, the instrument tends to follow tissue planes and to dissect fat and other soft tissues selectively. We performed a prospective, randomized, controlled trial in 73 patients comparing the safety and efficacy of a prototype ultrasonic dissector with that of electrosurgery and laser during laparoscopic cholecystectomy. Randomization was as follows: ultrasonic dissector, 37 patients; electrosurgery, 21 patients; and laser, 15 patients. The results were not different with respect to patient characteristics, amount of blood loss, technical difficulties, length of hospital stay, or return to work. Subjectively, the ultrasonic dissector was thought to be of special value in isolating the hilar structures, particularly when they were edematous or embedded in fat. The ultrasonic dissector disintegrated the fat, which was rapidly cleared up the suction channel, allowing the cystic duct and artery to be bared with less risk of injury. We concluded that the ultrasonic dissector has unique attributes that contribute to the ease and safety of laparoscopic cholecystectomy.  相似文献   

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